1. Field of the invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a transflective liquid crystal display device and a method of manufacturing the same.
2. Description of Related Art
In general, liquid crystal displays are divided into transmissive LCD devices and reflective LCD devices according to whether the display uses an internal or an outer light source.
A typical transmissive LCD device comprises a liquid crystal panel and a back light device. The liquid crystal panel includes upper and lower substrates with a liquid crystal layer interposed therebetween. The upper substrate has a color filter, and the lower substrate has a thin film transistor (TFT) as a switching element. An upper polarizer is arranged on the upper substrate of the liquid crystal panel, and a lower polarizer is arranged between the lower substrate of the liquid crystal panel and the backlight device.
At this time, the two polarizers have a transmittance of 45%, the two substrates have a transmittance of 94%, the TFT array and the pixel have a transmittance of 65%, and the color filter has a transmittance of 27%. respectively. Therefore, the transmisive LCD device gets to have about a transmittance of 7.4% as seen in FIG. 1 which shows a transmittance after light passes through each layers. For such a reason, the transmissive LCD device requires a high brightness and thus an electrical power consumption by the backlight device increases. In order to supply a sufficient power to the backlight device, a relatively heavy battery is employed, and there still exits a problem that the battery can not be used for a long time.
In order to overcome the problem described above, the reflective LCD has been developed. Since the reflective LCD device uses ambient light, it is easy to carry. Also, the reflective LCD device is superior in aperture ratio than the transmissive LCD device.
FIG. 2 is a plan view illustrating a typical reflective LCD device. As shown in FIG. 2, the reflective LCD device includes gate lines 6 and 8 arranged in a transverse direction, data lines 2 and 4 arranged in a longitudinal direction perpendicular to the gate lines 6 and 8, and thin film transistors xe2x80x9cSxe2x80x9d (TFTs) near cross points of the gate line 8 and the data line 2. Each of the TFTs xe2x80x9cSxe2x80x9d has a gate electrode 18, a source electrode 12 and a drain electrode 14. The data electrode 18 extends from the data line 2, and the gate electrode 18 extends from the gate line 8. The reflective LCD device further includes reflective electrodes 10. The reflective electrode 10 is electrically connected with the drain electrode 14 through a contact hole 16 and is made of a metal having a good reflectance.
By the way, the reflective LCD device has a problem that it is affected by its surroundings. For example, the brightness of ambient light in an office differs largely from that of the outdoors. Also, even in the same location, the brightness of ambient light depends on the time of day (e.g., noon or dusk).
In order to overcome the problem described above, a transflective LCD device has been developed. FIG. 3 shows a conventional transflective LCD device. As shown in FIG. 3, the conventional transflective LCD device includes gate lines 40 arranged in a transverse direction, data lines 20 arranged in a longitudinal direction perpendicular to the gate lines 40, thin film transistors xe2x80x9cTxe2x80x9d (TFFs) located near the cross points of the gate and data lines 40 and 20. Each of the TFTs xe2x80x9cTxe2x80x9d includes a gate electrode 34, a source electrode 30 and a drain electrode 32. The gate electrode 34 is extended from the gate line 40, and the source electrode 30 is extended from the data line 20. The conventional transflective LCD device further includes a reflective electrode 37 and a pixel electrode 39 connected with the drain electrode 32 through a contact hole 36. The reflective electrode 37 has a light transmitting hole 104 for transmitting light.
A method of manufacturing the conventional transflective LCD device is explained in detail below. FIGS. 4A through 4G are processing views illustrating a method of manufacturing the conventional transflective LCD device. As shown in FIG. 4A, a metal layer is deposited on a transparent substrate 1 and patterned into a gate electrode 34. As shown in FIG. 4B, a gate insulating layer 20 is formed on the exposed surface of the substrate 1 while covering the gate electrode 34. The semiconductor layer 22 is formed over the gate electrode 34. Sequentially, as shown in FIG. 4C, source and drain electrodes 30 and 32 spaced apart from each other are formed on the semiconductor layer 22. Then, as shown in FIG. 4D, a first passivation film 24 is formed on the exposed surface of the substrate 1 while covering the source and drain electrodes 30 and 32. A predetermined portion of the drain electrode 32 is exposed and thus a first contact hole 36 is formed. Next, as shown in FIG. 4E, an opaque conductive layer is deposited on the first passivation film 24 and patterned into a reflective electrode 37, forming a light transmitting hole 104 and contacting the drain electrode 32 through the first contact hole 36. As shown in FIG. 4F, a second passivation film 38 is formed on the exposed surface of the substrate while covering the reflective electrode 37. A second contact hole 36xe2x80x2 is formed at a location corresponding to the first contact hole 36. Finally, as shownn in FIG. 4G, a transparent conductive layer is deposited on the whole surface of the substrate 1 and patterned into a pixel electrode 39, contacting the reflective electrode 37 through the second contact hole 36xe2x80x2. Therefore, most of the important components of the conventional transflective LCD device are completed. At this point, the step of depositing the second passivation film 38 is optional, and therefore the second passivation film 38 may be not formed so that the pixel electrode 39 may contact the reflective electrode 37 directly. However, when the step of depositing the second passivation film 38 is omitted, a line defect such as a line open of the reflective electrode 37 may occur due to an etchant during patterning the transparent conductive layer into the pixel electrode 39.
As described above, the method of manufacturing the conventional transflective LCD device is very complex and thus requires a lengthy processing time. In order to reduce the number of the processes, if the step of forming the second passivation film 38 is omitted, as described above, there comes a problem that a line defect such as a line open of the reflective electrode 37 may occur due to an etchant during patterning the transparent conductive layer into the pixel electrode 39. Therefore, the conventional method of the transflective LCD device leads to a low production yield.
For the foregoing reasons, there is a need for a method of manufacturing a transflective LCD device by a simple process.
To overcome the problems described above, preferred embodiments of the present invention provide a transflective liquid crystal display device which can be manufactured with a high production yield by a simple process and a method of manufacturing the same.
The preferred embodiments of the present invention provide a transflective LCD device having a good resolution.
In order to achieve the above object, a transflectuive liquid crystal display device according to a preferred embodiment of the present invention includes a first transparent substrate and a second transparent substrate. The second substrate has a color filter and spaced apart from the first transparent substrate. The transflective liquid crystal display device further includes a liquid crystal layer interposed between the first and second transparent substrate and a gate electrode arranged on the first transparent substrate. The transflective liquid crystal display device further includes a reflective electrode arranged on the transparent substrate and spaced apart from the gate electrode The reflective electrode has a light transmitting hole. The light transmitting hole transmits light. The transflective liquid crystal display device further includes a first insulating layer arranged on the first transparent substrate while covering the gate electrode and the reflective electrode and a semiconductor layer having first and second ends and being arranged over the gate electrode. The transflective liquid crystal display device further includes a source electrode and a drain electrode. The source electrode overlaps the first end portion of the semiconductor layer and the drain electrode is spaced apart from the source electrode, overlapping the second end portion of the semiconductor. The transflective liquid crystal display device further includes a second insulating layer. The second insulating layer covers the source and drain electrodes and has a first contact hole located on a predetermined portion of the drain electrode. The transflective liquid crystal display device further includes a transparent electrode. The transparent electrode is arranged over the reflective electrode and contacts the drain electrode through the first contact hole and covers a portion of the second insulating layer corresponding to the light transmitting hole. The transflective liquid crystal display device further includes a backlight device. The backlight device supplies light toward the light transmitting hole.
The gate electrode and the reflective electrode are made of the same material. The reflective electrode is made of an opaque material. The transparent electrode is a pixel electrode. The pixel electrode is made of one of indium tin oxide and indium zinc oxide. The first and second insulating layer have a second contact hole on a predetermined portion of the reflective electrode so that the pixel electrode electrically contacts the reflective electrode through the second contact hole. The light transmitting hole is located on a central portion of the reflective electrode. The light transmitting hole has one of a circular shape and a rectangular shape. The transflective liquid crystal display device further includes lower and upper polarizers. The lower polarizer is arranged between the first transparent substrate and the backlight device, and the upper polarizer is arranged on the second transparent substrate.
In another aspect, a transparent liquid crystal display device according to the preferred embodiment of the present invention includes first and second gate lines spaced apart from each other and arranged in a transverse direction and first and second data lines spaced apart from each other and arranged in a longitudinal direction perpendicular to the gate lines. The transflective liquid crystal display device further includes a thin film transistor arranged near the cross point of the first gate line and the first gate line. The thin film transistor has a gate electrode, a source electrode and a drain electrode. The gate electrode is extended from the first gate line, and the source electrode is extended from the first data line. The transflective liquid crystal display device further includes a reflective electrode. The reflective electrode extends from the second gate line and has a light transmitting hole. The light transmitting hole transmits light. The transflective liquid crystal display device further includes a pixel electrode. The pixel electrode is electrically connected with the drain electrode and covers the light transmitting hole. The transflective liquid crystal display device further includes an insulating layer. The insulating layer is arranged between the reflective electrode and the pixel electrode.
The gate line and the reflective electrode are made of the same material. The reflective electrode is located in the form of an island on a central portion of a region defined by the gate and data lines, and the light transmitting hole surrounds the reflective electrode.
In another aspect, a method of manufacturing a transflective liquid crystal display device according to the preferred embodiment of the present invention includes depositing a metal layer on a transparent substrate; patterning the metal layer into a gate electrode and a reflective electrode, the gate electrode and the reflective electrode spaced apart from each other, the reflective electrode having a light transmitting hole, the light transmitting hole transmitting light; forming a first insulating layer on an exposed surface of the transparent substrate and covering the gate electrode and the reflective electrode; forming a semiconductor layer over the gate electrode; forming source and drain electrodes, the source and drain electrodes spaced apart from each other, the source electrode overlapping a first end portion of the semiconductor layer, the drain electrode overlapping a second end portion of the semiconductor layer; forming a second insulating layer over the whole surface of the transparent substrate and covering the source and drain electrode; and forming a first contact hole on a predetermined portion of the drain electrode; forming a pixel electrode covering a portion of the first insulating layer corresponding to the light transmitting hole, the pixel electrode containing the drain electrode through the first contact hole.